Waterbed mattresses of the most elemental form comprise two juxtaposed layers of plastic material with the edges directly or indirectly sealed together to form a bag. It has been proposed to provide internal baffle structures for the purpose of damping wave motions that occur when the weight load on the mattress is other than at rest.
One of the most successful structures is one that utilizes a series of individual bladders attached to the top and bottom mattress layers or walls. Each bladder is made of a pair of sheet plastic disks peripherally welded together. The disks are centrally attached to the respective mattress plies at places located inwardly of the periphery. When the mattress is filled with fluid, the disks of the bladder separate and the bladder assumes a generally biconical form. The bladder is open, as by a radial slit, to allow free passage of water into and out of the bladder. The resisted movement of water into and out of the bladder has a damping effect. Moreover, the bladders themselves form baffles in the mattress to assist the damping function. Such a structure is shown and described in said above-identified patent application. FIGS. 1 and 2 herein show such prior art mattress.